Seth Rudetsky is a walking google of the Broadway Theatre. A musician, stand-up comic, actor, writer and radio host, he is a Grammy and Emmy nominee.

Broadway @ Leicester Square is an attempt to recreate live what he does on his daily radio show on Sirius/XM in the US. It involves a seamless mix of intimate behind the scenes stories from Broadway's biggest stars with live performances by them, with him as the expert accompanist on the piano. His wit is razor sharp but he's never cruel and his shows (you can also find him on YouTube) are like impromptu spontaneous jams between friends. They are warm and friendly and aimed at those who know and love the subject. There is no dumbing down here. They are what chat shows were like before they became mired in product plugging and PR. Rudetsky manages to ask probing and revealing questions which conventional interviewers would never get away with and this and some glorious live performances are the key to their success.

He successfully brought the format to London twice before, first with Patti LuPone and last year with Audra McDonald. For his third live guest he chose John Barrowman.

Barrowman is an extraordinarily gifted singer with a solid musical theatre pedigree but is better known by the wider public for the TV shows Arrow, Torchwood and Doctor Who.

Born in Glasgow, he took up singing as a precocious child after his father's job relocated the family to the Midwest. He returned as an adult and was quickly discovered and made his professional stage debut in 1989 cast as the co-lead opposite Elaine Paige in a hit West End production of Cole Porter's Anything Goes. Quite a start. He career then took off with hit roles in musicals, in concert and subsequently on TV.

Normally Rudetsky is the camp outrageous one but he met his match here with Barrowman who re-defines gregarious. Rudetsky just had to press play and Barrowman was off telling tales of his childhood performances, his amazing break through and gossipy titbits about working with Lloyd Webber or Cameron Mackintosh or Sondheim.

He also talked movingly about the challenges he had in coming out, when young handsome male leads were seriously dissuaded from doing so, and this was not that long ago. Barrowman, rather like Ian McKellen, has blossomed since coming out, finding a new confidence in his performances. This was in evidence as soon as he stopped chatting got up to sing. He sang everything from Joni Mitchell to Lena Zavaroni and admitted how Sondheim had revealed to him that he thought he'd nailed the part of Bobby in Company like no other. He played it to great acclaim at Kennedy Center in Washington. Quite a compliment.

Barrowman's voice is sublime (he appears to have perfect pitch) but what's changed is that his interpretations have matured and mellowed. Here it was like someone getting up at a party and wowing everyone with their vocal ease but here of course it's grounded in years of experience and training. He even gave us 'Loch Lomond', which made us all feel sentimental and Scottish, even if we weren't.

The net result of this 3 concert set was to beg the question why isn't he getting cast in more musical theatre roles now. There are very few who can match him vocally and a good director would rein in the outrageousness.